WASHINGTON (AP) — After an 18-month investigation into Operation Fast and Furious, a Republican congressional draft report concludes that five officials at the Bureau of Alcohol, Tobacco, Firearms and Explosives share much of the blame for what went wrong with the gun-smuggling probe in Arizona.

The first of what will be three reports says many people in the chain of command at ATF are responsible, but the investigation singled out five key figures in the controversy, ranging from the special agent in charge of the ATF’s Phoenix field division up to the agency’s director.

In Operation Fast and Furious, agents employed a controversial tactic called gun-walking — allowing low-level “straw” buyers in gun-trafficking networks to proceed with loads of weapons that they purchased at gun shops in Arizona. The tactic was designed to track guns to major weapons traffickers and drug cartels, but many of the weapons weren’t tracked and wound up at crime scenes in Mexico and the U.S., including the site of a shootout on the U.S. side of the border that resulted in the death of a border agent, Brian Terry.

“Suspects continued to acquire weapons under ATF surveillance at an alarming rate,” said the report. “In the spring of 2010, concern was mounting among ATF leadership in Washington about the large volume of weapons being sold under Fast and Furious. The case became so large that ATF Deputy Director, William Hoover, requested an exit strategy for the case — something he had never done before.”

The operation nonetheless continued into the fall of 2010.

The former head of the ATF, Kenneth Melson, bears a significant measure of responsibility for failing to ensure that the agency’s headquarters personnel adequately supervised the Phoenix field division, says the report compiled by staffers for Rep. Darrell Issa, R-Calif., and Sen. Chuck Grassley, R-Iowa. The report also says:

• Bill Newell, the special agent in charge in Phoenix for several years, was a major promoter of the strategy in Fast and Furious. The report said Newell failed to understand the basic legal standards needed for interdicting firearms and questioning potential suspects, a shortcoming that prevented interrogation, disruption and possible arrest of straw purchasers.

• Deputy Assistant Director William McMahon knew that no operational safeguards were in place to prevent the firearms from traveling to Mexico, yet made no effort to stop the flow of guns, believing that it was not his job to interfere in Newell’s investigations.

• Assistant Director Mark Chait and his superior, Hoover, had several opportunities to put an end to the operation but failed to do so. Hoover knew that Newell had employed risky tactics in the past yet failed to monitor him closely.

Fast and Furious identified more than 2,000 weapons suspected of being illicitly purchased. Some 1,400 of them have yet to be recovered.